re PR ada/21346 (Ada.Directories.Compose raises exception if Containing_Directory is empty string)

gcc/ada/
	PR ada/21346
	* a-direct.adb (Compose): Containing_Directory can be an empty string.

    gcc/testsuite/
	PR ada/21346
	* gnat.dg/compose.adb: New test.

From-SVN: r130692

gcc/ada/ChangeLog

@@ -14,6 +14,9 @@
 	when an access to constant is used to initialize an access
 	value.
 
+	PR ada/21346
+	* a-direct.adb (Compose): Containing_Directory can be an empty string.
+
 2007-12-07  Olivier Hainque  <hainque@adacore.com>
 
 	PR ada/34173

gcc/ada/a-direct.adb

@@ -155,7 +155,9 @@ package body Ada.Directories is
    begin
       --  First, deal with the invalid cases
 
-      if not Is_Valid_Path_Name (Containing_Directory) then
+      if Containing_Directory /= ""
+        and then not Is_Valid_Path_Name (Containing_Directory)
+      then
          raise Name_Error;
 
       elsif
@@ -176,7 +178,7 @@ package body Ada.Directories is
 
          --  Add a directory separator if needed
 
-         if Result (Last) /= Dir_Separator then
+         if Last /= 0 and then Result (Last) /= Dir_Separator then
             Last := Last + 1;
             Result (Last) := Dir_Separator;
          end if;

gcc/testsuite/ChangeLog

@@ -15,6 +15,9 @@
 
 	* gnat.dg/specs/access_constant_decl.ads: New test.
 
+	PR ada/21346
+	* gnat.dg/compose.adb: New test.
+
 2007-12-07  Olivier Hainque  <hainque@adacore.com>
 
 	PR ada/34173

gcc/testsuite/gnat.dg/compose.adb

@@ -0,0 +1,11 @@
+-- { dg-do run }
+with Ada.Directories;
+with Ada.Text_IO;
+
+procedure Compose is
+   Result : constant String := Ada.Directories.Compose (Name      => "foo",
+                                                        Extension => "txt");
+   pragma Unreferenced (Result);
+begin
+   null;
+end Compose;